1. Field of the Invention
The present invention relates to a combustion chamber of a two-stroke engine.
2. Description of the Related Art
In the combustion chamber of a two-stroke engine disclosed in U.S. patent application Ser. No. 215,420 to the same assignee, a pair of the intake valves is arranged on one side of a masking wall extending from the inner wall of the cylinder head toward the combustion chamber, and a pair of the exhaust valves is arranged on the other side of the masking wall. The masking wall masks the valve opening between the valve seat and the peripheral portion of the intake valve, which is located on the exhaust valve side, for the entire time for which the intake valve is open.
In this two-stroke engine, fresh air fed from the intake ports is prevented from instantaneously flowing out into the exhaust ports by the masking wall, and as a result, since the entire fresh air fed from the intake ports flows downward toward the top face of the piston along the inner wall of the cylinder bore, which is located beneath the intake valves, a good loop scavenging operation can be obtained.
Nevertheless, in this two-stroke engine, when the diameters of the intake valves are increased to increase the amount of fresh air fed into the combustion chamber, the flow of the fresh air stream into the combustion chamber from the peripheral portions of the intake valves, which are positioned furthest from the axis of the cylinder bore, is prevented by the inner wall of the cylinder head, and as a result, a problem arises in that it is difficult to increase the amount of fresh air fed into the combustion chamber.